JPH1138807A - Heat fixing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an improved fixing device capable of performing fixation at the low temp., and applicable to high speed fixation. SOLUTION: This belt system fixing device, consisting of a fixing roller R1, the heating roller R2 equipped with a heater inside the roller, an endless shape fixing belt B extended over between both rollers and the pressure roller R3 held in press contact with the fixing belt B from below, is constituted so as to form a nip over between contact points of the fixing roller R1 and the pressure roller R3, and the heating roller R2 and the pressure roller R3 by holding the fixing roller R1 and the heating roller R2 in counter press-contact with or abutting against the pressure roller R3 across the fixing belt B.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heat fixing device for fixing a toner image on a recording medium, such as a plain paper copier, a plain paper facsimile, and a printer, using an electrophotographic system, an electrostatic recording system, or the like. .

[0002]

2. Description of the Related Art In general, a fixing device which forms a toner image on a recording medium by an electrophotographic method or an electrostatic recording method and fixes the toner image on the recording medium by heat and pressure has been developed in recent years. Due to the problem described above, especially in the low-speed field, the surf fixing method is becoming widespread due to the advantage of shortening the rising time (heating time). In addition, in the heat roller fixing method that can handle from low speed to high speed range,
Japanese Patent Application Laid-Open No. 61-59 discloses a method for shortening the heating time by using a thin metal core roller and maintaining the mechanical strength.
381, Japanese Utility Model Application Laid-Open No. 56-7949,
Japanese Patent Application Laid-Open Nos. 8-278715, 8-286541, 8-314307, and the like. Further, Japanese Patent Application Laid-Open No. Hei 8-2
JP-A-86-535 discloses a fixing roller in which a fixing belt is stretched between a fixing roller and a heating roller, a pressure roller is provided to press the fixing roller from below via the fixing belt, and the heat of the belt is used as a preheating source. Japanese Patent Application Laid-Open No. 8-314303 discloses that a high-quality image can be obtained without using a release agent, and the type of the recording medium can be improved. Instead, a fixing device capable of fixing at a constant speed has been proposed. However, in the surf fixing method or the heat roller method, although the heating time is shortened, in order to melt and fix the toner on the recording medium, the surface temperature of the heating roller is set to 150 to 1
It is necessary to keep the temperature at a high temperature of 90 ° C., and from the viewpoint of energy saving, a method capable of lowering the temperature at the time of fixing and performing low-temperature fixing and a corresponding toner are required. Further, in the fixing belt method, although the releasability of the belt and the toner and the oil-less property are improved, the nip width is substantially formed only by the contact between the fixing roller and the pressure roller. Is small. Further, in the latter belt fixing method, since a pressure roller is disposed for each of the heating and fixing rollers, and a cooling member is disposed so as to contact and slide with the belt, the heat capacity of the entire apparatus increases, and the heating is performed. The power consumption at the time increases accordingly. Therefore, a more effective method has been desired in order to enable further low-temperature fixing.

[0003]

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide an improved fixing device which can fix at a low temperature and can cope with a high speed fixing in view of the above prior art.

[0004]

The object of the present invention is to provide a heating roller having a fixing roller and a heater inside the roller, an endless fixing belt stretched between the two rollers, A belt fixing device including a pressure roller that presses against a belt from below, wherein the fixing roller and a heating roller are pressure-contacted or abutted against the pressure roller via the fixing belt, and the fixing roller, the pressure roller, and the heating roller. A heat fixing device characterized in that a nip is formed between the contact point of the roller and the pressure roller. ", (2)" a heat fixing device having a heater inside the fixing roller and the roller and the both rollers. It has a stretched endless fixing belt and a pressure roller that presses against the fixing belt from below, and a nip formed between the fixing roller, the pressure roller, and the contact point of the heating roller is a recording medium. A belt fixing device for feeding and fixing paper, wherein an auxiliary heater is disposed on the nip entrance side and on a side of the recording paper to which an unfixed toner image is attached, and the internal heater and the auxiliary heater are provided. And (3) a nip where the recording medium to which the unfixed toner image adheres arrives at the heating roller. (1) characterized in that it is arranged on the entrance side of the part
Item 2. The heat fixing device according to item 2 or 3. (4) "(1) or (2) wherein the fixing roller and the pressure roller are covered with a heat-resistant elastic release layer.
Item 2. The heat fixing device according to Item 1. (5) The item (1), wherein the surface hardness of the elastic layer covered by the fixing roller is set smaller than the surface hardness of the elastic layer of the pressure roller. , (4), the heat fixing device according to any one of (4) and (6), wherein the fixing belt is formed by forming a heat-resistant elastic release layer on a surface of a base made of metal or heat-resistant resin. Item (1) or (2) above
Item 2. The heat fixing device according to Item 1. (7) The heat fixing device according to (2), wherein the auxiliary heater is a sheet heating element, and the sheet heating element is formed of a ceramic heating element. (8) "The sheet heating element is held around by a heat-resistant low-thermal-conductivity material supporting member around its surface, except for the surface facing the toner layer attached to the recording medium. (9) The heat-fixing device according to the item (2). ”(9)“ On the back side of the heat-conductive recording medium guide support plate disposed close to the planar heating element,
The heat fixing device according to the above item (2), wherein a support member made of a low heat conductive material is closely mounted. "
(10) The fixing and heating rollers are formed such that the diameter of both rollers is smaller than the diameter of the pressure roller, and the central arrangement angle of both rollers from the center of the pressure roller is set in the range of 60 ° to 90 °. The heating and fixing device according to the above mode (1) or (2). "

Hereinafter, the contents of the present invention will be described in detail. According to the present invention described in the above item (1), the fixing roller and the heating roller are configured and arranged so as to oppose or contact with the pressure roller via an endless fixing belt stretched between the two rollers. As a result, compared to the nip width formed by pressing the fixing roller and the pressure roller in the related art, the nip is substantially spread over the entire area between the contact points of the heating roller and the pressure roller and the fixing roller and the pressure roller. It is possible to form a width (long nip), so that the nip time is increased and the toner on the recording medium can acquire more heat, so that the toner having the same melting softening temperature is used. When compared with the conventional heat roller fixing method or the conventional belt fixing method, it is possible to obtain a fixed image even at a lower temperature.

Further, according to the present invention described in the above item (2), the fixing roller, a heating roller having a heater inside the roller, an endless fixing belt stretched between the two rollers, and pressed against the fixing belt from below. A belt fixing device that has a pressure roller and feeds and fixes recording paper as a recording medium to a nip portion formed between a contact point between a fixing roller and a pressure roller and a contact point between a heating roller and a pressure roller. By providing an auxiliary heater at the nip entrance side facing the unfixed toner image on the recording medium, the thermoplastic resin component contained in the toner absorbs radiant heat from the auxiliary heater just before entering the nip portion. In order to start softening and melting, fixing is performed by passing through the nip portion in this state, so that higher-speed fixing can be performed even when the nip portion is kept at a low temperature.

According to the third aspect of the present invention, the toner on the recording medium is inserted into the nip area by disposing the heating roller, which is one of the elements constituting the nip area, at the nip entrance side. In the initial stage, it begins to soften and melt, and is efficiently fixed on the recording medium while passing through the nip portion where a sufficient nip time is secured, and the fixing roller side is already in the cooling process. Offset to the belt side hardly occurs.

Further, according to the present invention of the above item (4), since the heat-resistant elastic body is coated on the fixing roller and the pressure roller, the nip region formed by the pressure contact between the two rollers is
It is possible to form a high-pressure nip area having a higher pressing force as compared with a nip portion formed by contact between the belt and the pressure roller before this area, so that the toner is more strongly recorded in this area. Immobilized on media. Further, the fixing roller and the pressure roller are covered with a heat-resistant elastic body, and friction is generated between the two rollers by applying pressure through the belt, so that the fixing roller can be a driving roller and the other can be a driven roller. Therefore, a simple device configuration can be achieved.

Further, in the present invention of the above item (5), since the surface hardness of the elastic layer coated on the fixing roller is smaller than the surface hardness of the elastic layer of the pressure roller, the high-pressure nip area formed on the nip exit side is formed. Then, the recording medium is in a state along the outer peripheral surface of the pressure roller, and is discharged from the nip exit in a direction away from the fixing belt. As a result, the recording medium is smoothly separated from the surface of the fixing belt as it moves. Therefore, a separation claw is not required.

In the present invention of the above item (6), a heat-resistant elastic release layer, for example, a silicone rubber layer, is formed on the outer peripheral surface of a nickel electroformed belt or an endless substrate made of polyimide resin or the like as a fixing belt. It is known to use such a belt, but by using the belt, the releasability from the toner is improved and the surface of the belt can be prevented from being stained.

In the present invention as described in the above item (7), a fixed-type sheet heating element is provided at the nip entrance side, and the sheet heating element is constituted by a ceramic heating element having a fast temperature rising time. Therefore, the toner on the recording medium can be softened in a non-contact state, so that the holding temperature in the nip region can be significantly lowered as compared with the conventional hot roll fixing. Further, in an apparatus requiring high-speed fixing, the synergistic effect of the heating element and the extension of the nip time makes it possible to lower the temperature and reduce the power consumption as compared with the conventional method.

Further, in the present invention of the above item (8), the surface heating element is configured to be held by a heat-resistant material having low heat conductivity except for the surface facing the toner image, Heat diffusion to the surroundings can be prevented, and the heat absorption efficiency of the toner can be increased.

[0013] In the present invention of the above item (9), a support member made of a low heat conductive material is adhered to the back side of a thermally conductive recording medium support disposed close to the sheet heating element. With this arrangement, the radiant heat from the planar heating element can be efficiently received, and therefore, the recording medium can be preheated from the back surface.

Further, in the present invention described in the above (10), the diameters of the fixing roller and the heating roller are formed smaller than the diameter of the pressing roller, and the central arrangement angle of the two rollers from the center of the pressing roller is 60 degrees. Since the angle is set in the range of 90 ° to 90 °, the entire apparatus can be easily configured and downsizing can be easily realized. Further, when the arrangement angle of the two rollers is 60 ° or less, the nip length is shortened, and the low-temperature fixing effect is reduced. In order to prevent this, the diameter of the pressure roller may be increased, but miniaturization of the apparatus is hindered. Further, when the arrangement angle of the two rollers is 90 ° or more, the angle of insertion and discharge of the recording medium into and out of the nip portion is increased, which hinders the apparatus configuration and separability.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be specifically described below with reference to the drawings. The fixing device of the present invention is provided in an image recording apparatus such as a laser printer or an electrophotographic copying machine that creates a black-and-white image, and can fix a black-and-white image well at a low temperature. However, the present invention is not limited to this, and can be used as a fixing device of a device that creates a full-color image.

FIG. 1 is a schematic configuration diagram of a cross section of a main part showing an embodiment of a fixing device according to the present invention described in the above item (1). In the figure, (B) is a fixing belt, (H) is a heater serving as a heating source, (R1) is a fixing roller, (R2) is a heating roll, (R3) is a pressure roller, and (G) is a recording medium (P). (S1) and (S2) are thermistors for performing temperature control and temperature detection. As shown in FIG. 1, the fixing belt (B) is stretched by a rotatable fixing roller (R1) and a heating and tension roller (R2), and the fixing roller (R1) is fixed to the fixing belt (B).
Is pressed against the pressure roller (R3), and the heating roller (R3) is pressed.
2) Similarly, the pressure roller (R) is sandwiched between the fixing belt (B).
Contact 3). The fixing roller (R1) is rotationally driven by a drive source such as a motor (not shown), and the rotation of the fixing roller (R1) prevents the fixing belt (B) from slipping or loosening in the clockwise direction indicated by an arrow in the drawing. Stable rotation. Further, the heating roller (R2) and the pressure roller (R3) are driven to rotate by the rotation of the fixing belt (B). Due to these rotations, the recording medium (P) to which the unfixed toner image (T) adheres is moved in the direction of the arrow in the drawing, and the toner image surface contacts the fixing belt (B). The pressure roller and the long nip formed between the contact points of the heating roller and the pressure roller pass together with the fixing belt (B).

FIG. 3 is a schematic sectional view of a main part of an embodiment of a fixing device corresponding to the second embodiment of the present invention. In FIG. 3, the auxiliary heater (SH) includes a sheet heating element (CH) and a heat-resistant support member (SP). An opening is provided in a part of the heat-resistant support member (SP), and a thermistor (S3) for controlling the temperature of the sheet heating element (CH) is provided in the opening.
H). Also, (B
P) is a low thermal conductive support closely mounted on the back surface side of the metallic guide support plate (G). The running state of the recording medium (P) in the configuration of FIG. 3 is such that the sheet heating element (the fast rising temperature) which is a component of the auxiliary heater (SH) has a high temperature before the toner image on the recording medium is inserted into the nip area. CH)
Radiated heat and the reflected heat from the metal guide support plate (G) are efficiently received and become a softened state or a molten state, so that a good fixed image can be obtained only by applying a low-temperature pressing force in the nip region. By controlling the amount of power to the sheet heating element (CH) and the heating roller (H), power consumption can be reduced even in high-speed fixing as compared with the conventional fixing method.

As shown in FIGS. 1 and 3, a 600 W heater is provided inside the heating and tension roller (R2) as a heating heater (H). Further, it is possible to additionally provide a heater inside the pressure roller (R3). The heating roller (R2) is made of a hollow aluminum tube as shown in FIG. 2, and is made of a heat-resistant resin at both axial ends to prevent the fixing belt (B) from shifting. It has a collar (C) having a taper of 2 to 6 ° which is the same as the diameter of the aluminum tube at the portion in contact with the portion and whose diameter increases toward the opposite ends.

The fixing roller (R1) and the pressure roller (R)
3) is constituted by providing a heat-resistant elastic layer on the surface of a thin iron core, and the pressure roller (R3) is fixed to the fixing roller (R) via a fixing belt (B) by a spring (not shown).
Pressurized to 1). The heat-resistant elastic layers of the fixing roller and the pressure roller are formed on a pressure-bonding portion between the fixing roller (R1) and the pressure roller (R3) in order to enhance the releasability of the toner image (T) from the fixing belt. Since the nip shape is configured to be convex with respect to the surface of the recording medium (P) where the toner image (T) is attached, the pressure roller (R3) has a higher hardness than the fixing roller (R1). High elastic layer is used.
The fixing roller (R1) is provided with a silicone foam having a thickness of 3 mm and a rubber hardness of 30 ° on the surface of the core metal, and the pressure roller (R3) has a thickness of 1 mm and a rubber hardness of 20 to 3 on the core metal surface.
A silicone rubber layer of 0 ° is provided and a thickness of 30 μm
A PFA tube of m to 50 μm is provided.

The fixing belt (B) has a thickness of 30 to 5 for example.
A 50-150 μm thick silicone rubber layer is provided on the outer peripheral surface of an endless nickel belt formed by electroforming 0 μm,
The outer peripheral surface is subjected to mold release treatment with PFA or fluororesin, or a 50 to 150 μm silicone rubber layer is provided on the outer peripheral surface of an endless belt made of polyimide resin having a thickness of 60 to 100 μm, or the outer peripheral surface is formed with PFA or fluororesin. The mold release treated is used.

In the apparatus shown in FIGS. 1 and 3, the fixing belt (B) is provided with a heat-resistant elastic release layer of silicone rubber of 120 μm on the outer peripheral surface of a nickel electroformed endless belt having an inner diameter of 70 mm and a thickness of 40 μm. I have. The sheet heating element (CH) which is a component of the auxiliary heater (SH) in FIG.
Metallic Si is dispersed as a conductive material in a powdered insulating material based on ₂ O ₃ · SiO ₂ , and a self-heating ceramic heating element fired at a high temperature is extended to both ends on the electrode mounting part in the belt axis direction. It is formed in a plate shape having a length of 2 mm and a heating distance of 50 mm in the recording medium traveling direction, and is spaced apart from the opposed recording medium (P) by 3 to 5 mm.

The sheet heating element (CH) is made of PPF (polyphenylene sulphite) or PEE to prevent thermal diffusion except for the surface facing the toner image on the recording medium.
K (polyetheretherketone) and other supporting members (SP) made of a heat-resistant resin
The thermistor (S3) is attached to a part of P), and the temperature is controlled by controlling the amount of electricity to the sheet heating element (CH) according to the temperature detected by the thermistor (S3). ing.

The recording medium guide support plate (G) shown in FIG. 3 is made of a metal plate such as aluminum, iron, nickel or the like, and the back surface thereof receives the radiant heat from the sheet heating element (CH). A heat-resistant resin such as PPF or PEEK is provided in close contact with the recording medium (P) so that the recording medium (P) can be preheated from the back side when passing through the recording medium (P).

As shown in FIGS. 1 and 3, the pressure roller (R) of the fixing roller (R1) and the heating roller (R2) is used.
When the arrangement angle θ with respect to 3) is 60 ° or less as described above, the fixing temperature can be reduced as compared with the conventional roller fixing method or the like, but the effect is small, and the fixing property using the same fixing speed and toner is used. As a result, the effect of reducing the surface temperature of the belt (B) was 5 ° or less as compared with the surface temperature of the fixing roller in the roller fixing method. In contrast,
It was found that the effect of reducing the fixing temperature when θ was set in the range of 60 to 90 ° was 20 ° C. or more.

Table 1 below shows, as an experimental example, a comparison of the fixing characteristics between the long nip belt (LNB) fixing method shown in FIG. 1 and the conventional roller fixing method.
Here, in the LNB method, the fixing roller diameter was 25 mm, the heating roller diameter was 24 mm, θ = 65 °, and the surface pressure between the fixing roller (R1) and the pressure roller (R3) was 1.5 kg / cm ² . As a result, the fixing roller (R1) and the pressure roller (R
The width of the high pressure nip area formed by 3) is 10 mm, and the total effective nip width is about 27 mm. Further, in the conventional roller fixing method, the fixing roller has a PT
FE (polytetrafluoroethylene) was coated, and the pressure roller was formed by forming a silicone rubber on an iron core bar, and the surface thereof was coated with PFA. Both of them were 40 mm in diameter and had a nip width of 4.5.
mm. The nip time was set to 50 ms in comparing the fixing performances of both types. Where L
The nip time in the NB method was intended for the high-pressure nip area width. At this time, the process speed of the roller system is 90 mm
/ S, 200 mm / s in the LNB system. Further, Ricoh PPC toner TYPE 8200 is used as the toner,
In both cases, oil application was not performed.

[0026]

[Table 1]

From the results shown in Table 1, it was found that in the NLB system, the fixing temperature could be lowered by about 20 ° C. or more even if the process speed was increased to twice or more that of the conventional roller fixing system. Further, when the auxiliary heater shown in FIG. 3 is combined, when the belt surface temperature is set to 100 ° C., and when the surface temperature of the sheet heating element (CH) is set to 140 ° C., a process speed capable of fixing is possible up to 300 mm / s. Thus, high-speed fixing can be performed at a lower temperature than the conventional method.

[0028]

As will be apparent from the detailed and specific description above, according to the present invention, a substantially large nip width can be formed and a large amount of heat can be supplied to the toner on the recording medium. A good fixed image can be obtained at a lower temperature as compared with a fixing method or the like, and the present invention shown in the above (2) ensures low-temperature fixability even when the process speed is increased. be able to. Further, according to the present invention as described in the above items (3), (4) and (5), the toner on the recording medium starts to soften and melt at the initial stage of being inserted into the nip region, and sufficiently passes through the long nip. High fixing energy. At the high-pressure nip at the nip exit side where the cooling process has started, the toner is tightly fixed on the recording medium, and the releasability from the belt is improved due to the difference in hardness between the elastic layer covered by the fixing roller and the pressure roller. Thus, the toner is reliably separated from the fixing belt, the occurrence of offset is prevented, and a stable high-quality fixed image can be obtained even in a low temperature region. Further, a belt itself having a release layer formed on the surface of a metal or heat-resistant resin substrate is known, but according to the invention of the above item (6), by using the belt as a fixing belt for a fixing device of the invention, The fixing belt and the toner are reliably and synergistically separated from each other to prevent the offset, prevent the belt from being stained, and obtain a stable high-quality fixed image. According to the present invention of the above (7) and (8),
Since the temperature rise time is faster and the amount of far-infrared heat generated is larger than that of a halogen lamp at the nip entrance side, a self-heating type planar ceramic heating element with good heat absorption efficiency of toner is placed on the recording medium. The surface other than the surface facing the toner is covered with a heat-resistant resin having low thermal conductivity to prevent heat diffusion. Therefore, by using the heating element as an auxiliary heater, even when the process speed becomes high, a stable high A fixed image of high quality can be obtained at a low temperature. In the present invention of the above item (9), since the heat-resistant resin having low thermal conductivity is closely attached to the back side of the recording medium support made of metal, the recording medium can be preheated more efficiently than the back side. It is possible to contribute to improvement. In the present invention of the above item (10), the nip length effective for low-temperature fixing is ensured by setting the arrangement angle of the fixing and heating rollers in the range of 60 to 90 ° with respect to the pressure roller, The insertion and ejection of the recording medium into and out of the nip portion are performed without any trouble, the releasability of the toner and the belt is improved, and the contribution to the miniaturization of the apparatus can be secured.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of a cross section of a main part showing an example of a fixing device of the present invention.

FIG. 2 is a front view showing an example of a heating and tension roller (R2) used in a fixing device according to the present invention.

FIG. 3 is a schematic configuration diagram of a cross section of a main part showing another example of the fixing device of the present invention.

[Explanation of symbols]

R1 Fixing roller R2 Heating and tension roller R3 Pressure roller B Fixing belt C Color H Heating heater S1 Thermistor S2 Thermistor S3 Thermistor G Guide support plate BP Low thermal conductive support P Recording medium T Toner SH Auxiliary heater CH Surface ceramic Heating element SP Heat-resistant support member θ Arrangement angle of fixing roller (R1) and heating roller (R2) with respect to pressure roller (R3)

Claims (10)

[Claims] 1. A belt fixing device comprising: a fixing roller; a heating roller having a heater inside the roller; an endless fixing belt stretched between the two rollers; and a pressure roller which presses the fixing belt from below. The fixing roller and the heating roller are pressure-contacted or abutted on the pressure roller via the fixing belt to form a nip between the fixing roller and the pressure roller and the contact point between the heating roller and the pressure roller. A heat fixing device characterized by comprising. 2. An image forming apparatus comprising: a fixing roller; a heating roller having a heater inside the roller; an endless fixing belt stretched between the two rollers; and a pressure roller for pressing the fixing belt downward from the fixing roller. A belt fixing device that feeds and fixes recording paper as a recording medium to a nip formed between a roller and a contact point between a heating roller and a pressure roller,
An auxiliary heater is provided on the nip entrance side and on the side of the recording paper on which the unfixed toner image is attached, and the internal heater and the auxiliary heater are used together to fix the unfixed toner image on a recording medium. A heat fixing device characterized by the above-mentioned. 3. The heat fixing device according to claim 1, wherein the heat roller is disposed at an entrance side of a nip portion where a recording medium to which the unfixed toner image adheres arrives. 4. The heat fixing device according to claim 1, wherein the heat roller and the pressure roller are covered with a heat-resistant elastic release layer. 5. The pressure roller according to claim 1, wherein a surface hardness of the elastic layer covered by the fixing roller is set smaller than a surface hardness of the elastic layer of the pressure roller. 3. The heat fixing device according to claim 1. 6. The heat fixing device according to claim 1, wherein the fixing belt has a heat-resistant elastic release layer formed on a surface of a base made of metal or heat-resistant resin. 7. The heat fixing device according to claim 2, wherein the auxiliary heater is a sheet heating element, and the sheet heating element is formed of a ceramic heating element. 8. The heat generating element according to claim 2, wherein the surface of the heat generating element is supported by a heat-resistant low heat conductive material supporting member except for a surface facing the toner layer attached to the recording medium. 3. The heat fixing device according to claim 1. 9. A support member made of a low heat conductive material is closely mounted on a back surface side of a support plate for a recording medium guide having good thermal conductivity arranged close to the planar heating element. Item 3. A heat fixing device according to Item 2. 10. The fixing and heating roller, wherein the diameter of both rollers is formed smaller than the diameter of the pressing roller, and the central arrangement angle of both rollers from the center of the pressing roller is 60 ° to 9 °.
3. The method according to claim 1, wherein the angle is set to 0 [deg.].
3. The heat fixing device according to claim 1.